One source I read said that it wasn't a lighter, but a lighter refill cannister. This makes more sense to me than a plain lighter, as a refill cannister stores a good deal more gas than a lighter, and under pressure. This tracks with the way the dryer door bursts open prior to the explosion, seemingly indicating that the cannister lost integrity and releases its compressed contents. The increase in pressure within the dryer causes the door to open, the mixture of gas with oxygen hits the right concentration and boom.
